The study, published in the international journal Sex & Marital Therapy, surveyed 1,207 men and concluded that 41% of guys have experienced post-coital dysphoria (PCD). As many as 20% have experienced it within the month of being surveyed.

"After sexual activity I get a strong sense of self-loathing about myself, usually I'll distract myself by going to sleep or going and doing something else or occasionally laying in silence until it goes away.

"I feel a lot of shame. I usually have crying fits and full on depressive episodes following coitus that leave my significant other worried, and every once in a while she has crying spells after the act, but hers are rarer."

"Because I typically don't want my partner worried, however, sometimes I hold in the sadness for hours until she leaves as we do not live together."

Man, that sucks. What sucks even more is they don't know what causes it.

Study co-author Professor Robert Schweitzer said it might simply be a "dopamine rebound effect." In other words, what goes up (your happiness level during sex) must come down. "But really that's just a hypothesis," he admitted.

Some solace in all this is that if you do feel bummed out after sex, know that you're not alone.